The purpose of this proposed work is to compare and contrast the biological interactions of microwaves and specific ancillary agents upon two in vivo membrane barrier systems. The primary function which will be measured is membrane permeability. This characteristic will be extensively examined for the blood brain barrier (BBB). Using dye and radioactive tracer compounds (Oldendorf procedure), the action of microwave irradiation on BBB permeability will be examined in the presence of agents known to alter its permeability. Agents such as morphine, CO2, electroshock, convulsant drugs and x-ray will be used concurrent with microwave exposure to evaluate possible synergistic effects of BBB permeability. Agents known to produce neurotoxic lesions of the brain such as gold thioglucose and Japanese Encephalitis Virus (JEV), will be used to assess the consequence of the increase in BBB permeability induced by microwave exposure. Since BBB changes are implicated in the development of tolerance to morphine, the effect of microwaves to disrupt tolerance may be another useful indicator. The second functional barrier system proposed for study is the liver bile barrier. The premeability of the biliary tree will, following microwave exposure, be assessed by the segmented retrograde intrabiliary injection (SRII) technique and by the measurement of intrabiliary pressures. As with the other systems, a variety of ancillary agents (bile salts and estrogens) will be examined for their possible synergistic interaction with microwave irradiation on the permeability characteristics of the biliary tree. One of the useful characteristics of this system is that bile flow increases with increase in liver temperature. This feature allows a biological monitoring system.